This project deals with a cytotoxic lymphocyte-mediator, lymphotoxin, elaborated by stimulated lymphocyte which appears to be involved in cellular immune reactions such as tumor immunity. More specifically: 1) The investigation deals with the interaction of this mediator with the target cell plasma membrane 2) The studies are concerned with previously demonstrated marked abberation in ribonucleic acid synthesis by lymphotoxin. This observation is now extended by examining the effect of a variety of inhibitors of RNA synthesis on lymphotoxin treated cells. 3) The research will deal with the part played by lymphotoxin in tumor cell destruction by cellular immune reactions in the intact animal. Additional studies are underway to examine the role of lymphotoxin on lymphocyte mediated cell destruction in tissue culture. 4) Observations have been completed on the binding kinetics of lymphotoxin to lymphotoxin sensitive and resistant target cells, which indicate that resistance can in part be explained by the absence of cellular lymphotoxin receptor. BIBLIOGRAPHIC REFERENCE: Kunitomi, G., Rosenau, W., Goldberg, M.L., and Burke, G.C. Alterations in RNA synthesis in lymphotoxin-treated target cells. Am. J. Path. 80:249-260, 1975.